v2.4.0.6
Supplemental Information On Oil And Gas Operations (Results Of Operations) (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]      
Oil, gas and NGL sales $ 8,315 $ 7,262 $ 6,097
Lease operating expenses (1,851) (1,689) (1,670)
Depreciation, depletion and amortization (2,248) (1,930) (2,108)
Reduction of carrying value of oil and gas properties     (6,408)
United States [Member]
      
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]      
Oil, gas and NGL sales 5,418 4,742 3,958
Lease operating expenses (925) (892) (997)
Depreciation, depletion and amortization (1,201) (998) (1,247)
General and administrative expenses (132) (133) (145)
Taxes other than income taxes (357) (319) (258)
Accretion of asset retirement obligations (34) (42) (53)
Income tax expense (1,005) (849) 1,800
Results of operations 1,764 1,509 (3,350)
Depreciation, depletion and amortization per Boe 6.94 6.11 7.47
Reduction of carrying value of oil and gas properties     (6,408)
Canada [Member]
      
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]      
Oil, gas and NGL sales 2,897 2,520 2,139
Lease operating expenses (926) (797) (673)
Depreciation, depletion and amortization (786) (677) (585)
General and administrative expenses (119) (83) (74)
Taxes other than income taxes (45) (40) (35)
Accretion of asset retirement obligations (57) (50) (38)
Income tax expense (250) (246) (210)
Results of operations 714 627 524
Depreciation, depletion and amortization per Boe 11.74 10.51 8.84
North America [Member]
      
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]      
Oil, gas and NGL sales 8,315 7,262 6,097
Lease operating expenses (1,851) (1,689) (1,670)
Depreciation, depletion and amortization (1,987) (1,675) (1,832)
General and administrative expenses (251) (216) (219)
Taxes other than income taxes (402) (359) (293)
Accretion of asset retirement obligations (91) (92) (91)
Income tax expense (1,255) (1,095) 1,580
Results of operations 2,478 2,136 (2,836)
Depreciation, depletion and amortization per Boe 8.28 7.36 7.86
Reduction of carrying value of oil and gas properties     $ (6,408)